What if — just maybe — we find extra-terrestrial life in the oceans of Europa, a little moon circling Jupiter? If we do, says writer Caspar Henderson, don't expect that oceanic alien to be very big. Or very scary. Or even very visible. Nothing like this ...

The "top predator" on Europa, Henderson reports, is likely to be "a fearsome creature with the mass of one gram." That's three one-hundredths of an ounce.

We wouldn't be able to talk to it. It wouldn't have much on its mind since creatures that small probably don't have minds.

The sad fact is extra-terrestrials are much less interesting than they used to be.

A hundred years ago, it was so different. Harvard astronomer Percival Lowell was describing "canals" on Mars built, he thought, by an intelligent race of thirsty Martians who were trying to channel melting water from the poles to dry cities on the Martian equator. What a tale!

Today? Today we've got a little robot sniffing the dry Martian air for a hint of microscopic life that may — or may not — be hiding in the Martian soil.

It's not just that we've given up hope of finding intelligent beings, it's worse than that. The life we now expect (or rather hope) to find is usually imagined as depressingly small, pebble-sized, or even smaller, like the period at the end of this sentence.

Yeah, that small.

Obvious And Unnecessary Aside

I know, I know, it would be enormously exciting to find life somewhere other than Earth, any kind of life, of any size — but I think it would be so much more fabulous if that life had heft — a body that weighed, oh, 100 pounds, that was four, five, six feet across. Something just a little ... umm, scary.

Well, it could happen.

Professor Dirk Schultze-Makuch and astrobiologist David Grinspoon have proposed the possibility of just such a creature. Schultze-Makuch is an environmental science professor at Washington State University and Grinspoon is an astrobiologist at the Denver Museum of Nature & Science; both are serious, well regarded scholars (even if Grinspoon fronts for a funk band called "House Band of the Universe.")

In 2005, they describe this large alien life form in a papercalled, "Biologically Enhanced Energy and Carbon Cycling on Titan?" and when I read what they wrote, suddenly I was, happily, frightened again!

Just to set this up, Titan is a moon that circles Saturn (In 2005, a probe landed there, and took pictures). It's very cold there, something like 180 degrees Celsius below freezing, and yet there seem to be lakes on its surface. You can see them in the photos ...

Those aren't water lakes. Water would freeze. They are presumed to be lakes of liquid ethane or methane, and several scientists, including NASA's Chris McKay proposed back in 2005 it's just possible there could be life in those lakes. Not water life, obviously, but acetylene or hydrogen eating creatures. After all, there are methane eaters here on earth, down near vents in our oceans, so why not on Titan?

Chris suggested that if we ever fly close, we should look for missing methane on Titan. If there's lots of methane and hydrogen in Titan's air and less on the ground, one possibility is: something on the ground (or in those lakes) is eating the stuff. And lo and behold, we did fly close by, and a series of papers published in 2010 found missing hydrogen and missing acytelene on Titan's surface. Just like Chris McKay hoped.

Does that mean there are methane eaters on Titan? No. Reporters got very excited for a day or two until the scientists and then Carolyn Porco, leader of the imaging team on the Titan project tweeted "Everyone: Calm down! It is by NO means certain that microbes are eating hydrogen on Titan. Non-bio explanations are still possible."

But methane eaters are still possible too.

And here's where my heart starts to beat fast. In their 2005 paper, Dirk Schultzs-Makuch and David Grinspoon said if one day methane eaters are found to exist on Titan, and if they swim around in very, very cold ethane lakes or oceans, and if those oceans don't have the pressure or weight of water, the cells in those critters might grow much larger than living cells on Earth. That's when they thrilled me. They used the H- word, as in "huge."

It's smack in the middle of this paragraph. In fact, I'll boldface it for you:

In an extremely cold, hydrophobic (but liquid) environment, surface/volume ratio considerations may be less constraining than at higher temperatures in polar solvents. Thus, life on Titan could involve huge (by Earth standards) and very slowly metabolizing cells, in which case biomass densities would be higher than calculated above.

That means one day, it's possible — not likely, but scientifically plausible — that we will get to meet a life form in our solar system that's not a puny, dumb little thing, but a huge dumb thing. Like dog-sized. Or maybe Volkswagen-sized. Yes, it would be very, very simple, probably an extremely dull life form, a floating giant egg of a thing, but it would be what we haven't dared dream about for the last 50 years: It would be big! And alive!